Species Diversity and Relative Abundance of Fisheries Resources Found in Beach Seine along the Central Coast of Ghana J. Aggrey-Fynn1* and R. Sackey-Mensah2 1 Department of Fisheries and Aquatic Sciences, University of Cape Coast, Cape Coast, Ghana 2 Fisheries Commission, Accra, Ghana *Corresponding author, Email: [email protected] Abstract The diversity and relative species abundance of fisheries resources were studied from Winneba to Cape Coast on the central coast of Ghana during December 2007 to May 2009. Samples of organisms were collected at random from beach seine landings during the study period. The fishes were counted and identified to the family and species levels. Ecological indices such as Shannon-Wiener diversity index, equitability and Sørenson’s similarity index were used to analyse the data. Specimens from Winneba, Saltpond and Cape Coast comprise 56 species belonging to 30 families. Carangidae, Haemulidae, Clupeidae and Sciaenidae were some of the families, where key species occurred during the study. The relative abundance of key organisms in the beach seine landings include Chloroscombrus chrysurus (26.0%) in 2007, Brachydeuterus auritus (22.8%) in 2008, Ilisha africana (14.7%) in 2008, Sardinella aurita (13.1%) in 2009 and Selene dorsalis (11.2%) in 2007. The organisms that were in low relative abundance were Acanthurus monroviae, Penaeus notialis, Galeoides decadactylus and Trichiurus lepturus. Shannon-Wiener diversity index, estimated in the study, ranged from 2.54 to 2.83. Species equitability range was 0.67–0.77, and the Sørenson’s similarity estimated ranged was 0.66–0.69. The estimations of fish species diversity and equitability were higher (H’ = 2.83; J’ = 0.77) during the 2009 study in the central coast of Ghana. The similarity indicators in the various paired periods during the study showed considerable similarity in the organisms that were exploited by the beach seine in the area. The study explains the linkage between the diversity and relative species abundance of the coastal fisheries resources and offshore marine resources in Ghana, and the need to regulate beach seine operations in order not to over exploit the juvenile stocks. Introduction 2003) and widely practiced on sandy beaches The Ghanaian waters, which form part of the of Ghana. It contributes 12% to the total Gulf of Guinea, is endowed with abundant artisanal fishery landings (Bannerman et al., fishery resource (Mensah & Quaatey, 2002; 2001). Mehl et al., 2004, 2005). The resources are The fish species composition of beach exploited by the industrial and the artisanal seine had been assessed in other areas of fishers. In Ghana, the artisanal fisheries Ghanaian coastal waters by Nunoo et al. contribute about two-thirds of the total (2007) and other unpublished reports by the annual marine production (MFRD, 2002). Directorate of Fisheries, Accra, Ghana. The The artisanal fishery is mostly practised in diversity of fish in Benya Lagoon and Kakum the nearshore areas in the form of inshore River Estuary (Blay, 1997), which are linked canoe and beach seine fisheries. The beach to the fisheries resources in the coastal waters seining is the common traditional fishing of the Central Region, Ghana, had been method, which is used all year round (MoFA, assessed. The central coastal zone happens to 2 West African Journal of Applied Ecology, Vol. 20 (1), 2012 Aggrey-Fynn and Sackey-Mensah: Species diversity and relative abundance of fisheries resources 3 be the longest coastline (330 km) and has the identifications were to the family and species highest concentration of brackish water levels. Various fish species were counted and systems; 65 as compared to that of western recorded for the estimation of proportions in 17 and eastern 16 (Yankson & Obodai, the sub-samples collected from the landings. 1999). These brackish water habitats are The relative abundance was calculated as the known to provide nursery and feeding number of organisms of a particular kind, grounds to vast number of marine fish indicating a percentage of the total number of species (Lasiak, 1984; Armah & Amlalo, organisms (Krohne, 2001). 1998; Nash & Santos, 1998; GCLME, Coastal fish species diversity was 2006). The study, therefore, seeks to update calculated by using the Shannon-Wiener fish species diversity and abundance records index (H1 ) as follows: in the coastal waters of the Central Region, H2 = - S pi (ln pi) ……..........……….. (1) which are very important to the Ghanaian where pi is the proportion of the ith species fisheries, and to serve as a contribution to the (Molles, 1999); the evenness (J1) of diversity baseline information on coastal fisheries was calculated from Pielou’s index (Pielou, resources. 1966) given as: 1 1 J = H / Hmax ……...........…………… (2) Materials and methods where Hmax = ln s, and s is the number of There are three coastal zones of Ghana, species in the community. Fish species which are Eastern (128 km), Central (330 similarity in 2007–2008, 2007–2009 and km) and Western (93 km) alongshore 2008–2009 were determined by Sørensen’s distance (Yankson & Obodai, 1999; EIA, coefficient (Cs) as follows: 2009). The fish species diversity and relative 2j Cs = a+ b (Krebs, 1999) …...………... (3) abundance were studied in the central coast where j is the number of fish species common (Fig. 1) of Ghana from Winneba to Cape to both paired years, and a and b are the Coast (5°19’N, 0°38’W and 5°05’N, number of species occurring in either of the inneba, Saltpond and Cape Coast fish landing beaches of central coast, Ghana coast, central of beaches landing fish Coast Cape and Saltpond inneba, 1°16’W), between the period December paired periods (Brower et al., 1990). W 2007 and May 2009. The Winneba-Saltpond waters is an area where the artisanal fish Results catch is high (MFRD, 1993), probably Nearshore fish species that were sampled linked to the suitable oceanographic from beach seine operations at Winneba, conditions in the area (Aggrey-Fynn, 2008) Saltpond and Cape Coast beaches are and numerous connected coastal brackish presented in Table 1. A total of 56 species, water systems. belonging to 30 families, were recorded in Fish specimens were collected at random the central coastal waters. The waters near from beach seine landings along the central Winneba recorded 28 species that occur in 18 families, whereas those near Saltpond and coast during the study period. Landing sites of location the showing Map 1. Fig. were Winneba, Saltpond and Cape Coast Cape Coast recorded 34 and 31 species each, (Fig. 1). Fish identification was done in the belonging to 20 families, respectively. laboratory using manuals (Schneider, 1990; Table 2 shows the number of organisms Kwei & Ofori-Adu, 2005). The caught from beach seine operations from 2 West African Journal of Applied Ecology, Vol. 20 (1), 2012 Aggrey-Fynn and Sackey-Mensah: Species diversity and relative abundance of fisheries resources 3 be the longest coastline (330 km) and has the identifications were to the family and species highest concentration of brackish water levels. Various fish species were counted and systems; 65 as compared to that of western recorded for the estimation of proportions in 17 and eastern 16 (Yankson & Obodai, the sub-samples collected from the landings. 1999). These brackish water habitats are The relative abundance was calculated as the known to provide nursery and feeding number of organisms of a particular kind, grounds to vast number of marine fish indicating a percentage of the total number of species (Lasiak, 1984; Armah & Amlalo, organisms (Krohne, 2001). 1998; Nash & Santos, 1998; GCLME, Coastal fish species diversity was 2006). The study, therefore, seeks to update calculated by using the Shannon-Wiener fish species diversity and abundance records index (H1 ) as follows: in the coastal waters of the Central Region, H2 = - S pi (ln pi) ……..........……….. (1) which are very important to the Ghanaian where pi is the proportion of the ith species fisheries, and to serve as a contribution to the (Molles, 1999); the evenness (J1) of diversity baseline information on coastal fisheries was calculated from Pielou’s index (Pielou, resources. 1966) given as: 1 1 J = H / Hmax ……...........…………… (2) Materials and methods where Hmax = ln s, and s is the number of There are three coastal zones of Ghana, species in the community. Fish species which are Eastern (128 km), Central (330 similarity in 2007–2008, 2007–2009 and km) and Western (93 km) alongshore 2008–2009 were determined by Sørensen’s distance (Yankson & Obodai, 1999; EIA, coefficient (Cs) as follows: 2009). The fish species diversity and relative 2j Cs = a+ b (Krebs, 1999) …...………... (3) abundance were studied in the central coast where j is the number of fish species common (Fig. 1) of Ghana from Winneba to Cape to both paired years, and a and b are the Coast (5°19’N, 0°38’W and 5°05’N, number of species occurring in either of the inneba, Saltpond and Cape Coast fish landing beaches of central coast, Ghana coast, central of beaches landing fish Coast Cape and Saltpond inneba, 1°16’W), between the period December paired periods (Brower et al., 1990). W 2007 and May 2009. The Winneba-Saltpond waters is an area where the artisanal fish Results catch is high (MFRD, 1993), probably Nearshore fish species that were sampled linked to the suitable oceanographic from beach seine operations at Winneba, conditions in the area (Aggrey-Fynn, 2008) Saltpond and Cape Coast beaches are and numerous connected coastal brackish presented in Table 1. A total of 56 species, water systems. belonging to 30 families, were recorded in Fish specimens were collected at random the central coastal waters. The waters near from beach seine landings along the central Winneba recorded 28 species that occur in 18 families, whereas those near Saltpond and coast during the study period.